Generally, in a rotary machine, such as a gas turbine or a steam turbine, a shaft seal device is used to prevent working fluid from leaking to the low-pressure side from the high-pressure side through an annular gap that is formed between a stationary portion and a rotatable portion. A non-contact labyrinth seal is widely used as one of such shaft seal devices. However, the non-contact labyrinth seal needs to be formed so that an end of a seal fin does not come into contact with a shaft even when the shaft is vibrated or excessively thermally deformed during a rotational transition (during starting, stopping, and the like). For this reason, a gap (a seal clearance) between ends of the seal fins needs to be large to some extent. Meanwhile, when the seal clearance is excessively large, working fluid leaks.
For example, PTL 1 discloses a shaft seal device that reduces the leakage of the working fluid. This shaft seal device includes a seal body in which flat thin plates having a predetermined width in an axial direction of a rotor are disposed in a circumferential direction of the rotor in the form of multiple layers.
In the seal device, inner periphery-side end portions of the thin plates come into contact with the rotor during stopping of the rotor. Meanwhile, during the rotation of the rotor, a floating effect acts on the thin plates by the effect of dynamic pressure, and the inner periphery-side end portions of the thin plates float from the rotor. Accordingly, during the rotation of the rotor, the thin plates do not come into contact with the rotor while the minimum clearance is formed between the rotor and the thin plates.